1. Filed of the Invention
The present invention relates to a light source structure for a signal indication lamp which is installed in, for example, a workplace, a parking lot and other potentially dangerous places in order to give visual warning signals.
2. Prior Art
Signal indication lamps are used in various places. They are installed on automatic machines, on robots and in production lines for indicating abnormalities of the machines and robots, thus assuring the safety of workers at the production line. They are also used for warning the shortage of material and the clogging of workpieces. When the lamps are used in a parking lot, they can indicate dangerous traffic conditions and that the parking is full.
FIG. 9 shows an example of a conventional signal indication lamp structure that uses LEDs as disclosed in Japanese Patent Application Laid-Open (Kokai) No. 57-93392.
In this prior art, a plurality of LEDs 71c are successively connected to one another to define a bar-shaped light source 71. A plurality of bar-shaped light sources 71 are disposed upright along a circle so as to define an indicator section 7. The indicator section 7 is mounted on a mounting table 73 and is covered by a filter case 72. The LEDs 71 are operated by a built-in drive circuit 74. In this prior art lamp as shown in FIG. 8, ninety-eight LEDs are outwardly disposed for projecting signal light toward the circumference thereof.
With the structure describe above, light emitted by the LEDs 71c is projected outwardly through the filter case 72; and when the signal indicator lamp is viewed from any viewing angle, the LEDs 71c in a plurality of bar-shaped light sources 71 are recognized as dots.
FIG. 10 shows another example of a prior art signal indicator lamp structure. This lamp structure is disclosed in the Japanese Utility Model Application Laid-Open (Kokai) No. 4-108806. In this signal indicator, the light from LEDs is not directly projected toward the circumference but is reflected toward the circumference by reflectors. In particular, the indicator includes a pair of upper and lower plural LEDs 81 disposed to face each other and a cylindrical support which has a bulged portion at the middle thereof. Reflectors 82 are provided on the bulged portion with upper reflectors facing the upper LEDs and the lower reflectors facing the lower LEDs. The LEDs 81 and the reflectors 82 are surrounded by a globe 83 that has diffusion lenses.
In this signal lamp, the light emitted from the LEDs 81 is reflected toward the circumference of the lamp by the reflectors 82 and projected through the globe 83 toward the environment surrounding the lamp. When the signal indicator lamp is viewed from any viewing angle, light sources are recognized as generally plain surfaces that correspond to the reflectors 82.
Other similar types of signal lamps are also known. For example, Japanese Utility Model Application Laid-Open No. 3-12419 discloses a structure in which wired substrates, each having numerous LEDs embedded therein, are disposed in layers. Japanese Utility Model Application Laid-Open No. 3-6675 discloses a structure in which wired substrates, each having numerous LEDs embedded therein, are disposed in the shape of a polygonal column.
In all of the above described conventional light source structures adapted for signal indicator lamps, light emitted from the LEDs may be directly projected toward the environment or simply reflected toward the environment. As a result, as shown in FIG. 9, numerous LEDs are required to enlarge the light source to be recognized. However, in accordance with the conventional structure, the light source is only recognized as an aggregation of numerous dots, which does not provide a pleasing look.
In accordance with the structure shown in FIG. 10, the light from the LED light source is diffused by the globe 83. As a result, the light source is recognized as being rectangular with a generally plain surface, which results in a better look and an improved visibility. However, although there is a structural difference between the type in which the LED light is reflected and the type in which the LED light is directly irradiated, there is no difference with respect to the visibility between these different structures.
Furthermore, the signal indication lamp that uses LEDs as described above has a low power consumption and does not require the maintenance work which may be required for light bulbs that may burn out or may be readily damaged by vibration. However, due to the low brightness of the LED itself, numerous LEDs are required for practical use, and the increased number of LEDs results in increases in power consumption and heat generation. On the other hand, the use of LEDs with a high degree of brightness makes the light indication lamp expensive.